Aim of study: Modelling of forest growth and dynamics has focused mainly on pure stands. Mixed-forest management lacks systematic procedures to forecast the impact of silvicultural actions. The main objective of the present work is to review current knowledge and forest model developments that can be applied to mixed forests.Material and methods: Primary research literature was reviewed to determine the state of the art for modelling tree species mixtures, focusing mainly on temperate forests.Main results: The essential principles for predicting stand growth in mixed forests were identified. Forest model applicability in mixtures was analysed. Input data, main model components, output and viewers were presented. Finally, model evaluation procedures and some of the main model platforms were described.Research highlights: Responses to environmental changes and management activities in mixed forests can differ from pure stands. For greater insight into mixed-forest dynamics and ecology, forest scientists and practitioners need new theoretical frameworks, different approaches and innovative solutions for sustainable forest management in the context of environmental and social changes.Keywords: dynamics, ecology, growth, yield, empirical, classification.

Non-native forest tree species have been introduced in Europe since the 16th century, but only in the second half of the 20th century the significance of the seed source origin for their economic use was recognized, resulting in the establishment of numerous provenance trials at a national, regional, European and International level, as those led by IUFRO. Breeding programs have also been launched in the continent for the most economically important species. Aim of this work is the formulation of provenance recommendations for planting of five non-native tree species in Europe (Douglas fir, grand fir, Sitka spruce, lodgepole pine and black locust), based on the information obtained from twenty countries, in the frame of the EU FP-1403 NNEXT Cost Action. The survey revealed that official and non-official national recommendations, based on provenance research results, have been elaborated and followed at a different level and extend for the above five species, but only for Douglas fir recommendations exist in almost all the participating to the survey countries. The compilation of provenance recommendations across Europe for each species is presented in the current work. Besides the recommended introduced seed sources, European seed sources are also preferred for planting, due to ease of access and high availability of forest reproductive material. European breeding programs yielding genetic material of high productivity and quality constitute currently the seed source of choice for several species and countries. Consolidation of trial data obtained across countries will allow the joint analysis that is urgently needed to draw solid conclusions, and will facilitate the development of ‘Universal-Response-Functions’ for the species of interest, rendering possible the identification of the genetic material suitable for global change. New provenance trial series that will test seed sources from the entire climatic range of the species, established in sites falling within and outside the environmental envelopes of their natural ranges, are urgently needed to pinpoint and understand the species-specific climate constraints, as well as to correlate functional traits to the seed origin and the environmental conditions of the test sites, so that the selection of suitable forest reproductive material of non-native tree species in the face of climate change can be feasible.

Gospodarenje alohtonim vrstama ima tradiciju u hrvatskome šumarstvu, ali njihov potencijal se treba ponovno razmotriti i ocijeniti u novonastalim okvirima klimatskih promjena te rastućim potrebama društva za šumskim proizvodima i uslugama. Unatoč činjenici da svaka država ima svoj popis introduciranih vrsta, uključujući i Hrvatsku, autori prihvaćaju definiciju COST Akcije FP1403 NNEXT te rad baziraju na šumskim vrstama drveća kojima se prirodni areal nalazi izvan granica Europe. Ovaj pregledni rad doprinos je saznanjima o introdukciji i aktivnoj uporabi alohtonih vrsta u zemlji, a obuhvaća dostupne znanstvene i stručne studije te primjere uspješne uporabe u gospodarenju šumama. Zbog složenosti ove problematike autori će objaviti pregled rizika i izazova uporabe alohtonih vrsta u zasebnome radu. Dostupni podaci o prisutnosti alohtonih vrsta na pokusnim objektima te u šumarskoj praksi ukazuju kako se u praksi koristi tek manji broj vrsta (Tablica 1), dok su stvarni potencijal i njihove koristi daleko veće. Analiza podataka ukazuje kako su najzastupljenije alohtone vrste u šumarskoj praksi: Robinia pseudoacacia L. (12003.88 ha), Pinus strobus L. (3218.69 ha), Juglans nigra L. (2376.66 ha), F. pennsylvanica Marshall. i Fraxinus americana L.(1099.77 ha), Pseudotsuga menziesii (Mirb.) Franco. (393,05 ha) i L Quercus rubra. (51,99 ha). Podaci o proizvodnji šumskoga reprodukcijskog materijala navedenih vrsta ukazuje da rasadnička proizvodnja nije usklađena s potencijalom njihove uporabe u praksi. U radu se daje i iscrpan pregled različitih gledišta i koristi uzgoja alohtonih vrsta u Hrvatskoj. Samo neke od njih su (Slika 1, Tablica 2): nove mogućnosti proizvodnje visoko kvalitetnog drveta u kraćim ophodnjama, kao i drveta za bioenergiju, novih drvnih proizvoda i tehnologija; socijane koristi (mali i srednji poduzetnici, privatni šumoposjednici); povećanje stabilnosti i adaptabilnosti šumskih sastojina, ali samo u slučajevima velikih šteta i male plastičnosti i otpornosti domaćih vrsta; smanjenje intenziteta šumskouzgojnih radova, kao i uloženih sredstava na pripremi staništa prilikom pošumljavanja; ostvarivanje većih mogućnosti uporabe zapuštenoga poljoprivrednog zemljišta i ostalih prikladnih površina; sanacija progala ili većih površina nakon šteta u sastojinama domaćih vrsta (npr. obične smreke); supstitucija osjetljivih vrsta otpornijim i plastičnijim vrstama (mogućnosti mješovitih ili obogaćenih sastojina otpornijim alohtonim vrstama) te umanjenje negativnog djelovanja biotskih i abiotskih čimbenika. Njihova uporaba u sanaciji površina te konverziji degradiranih i devastiranih šuma pruža nove mogućnosti posebice na područjima s nepovoljnim ekološkim uvjetima, za koja se predviđa da će biti najpogođenija područja Hrvatske u budućnosti. Alohtone vrste mogu osigurati i niz opće korisnih funkcija šuma (npr. povećanje vezanja ugljika, fitoremedijacija zagađenih tala). Zbog složenosti problematike preporučujemo da se odluke o uporabi alohtonih vrsta donose na osnovi usporedbe s domaćim vrstama za svako stanište te na osnovi pregleda potencijalnih koristi, ali i rizika i izazova. Ističemo kako pojedine alohtone vrste treba poticati, dok neke zbog svoga invanzivnog potencijala trebaju biti strogo ograničene. Uporaba visokoproduktivnih, otpornijih i plastičnijih alohtonih vrsta predstavlja nova šumskouzgojna rješenja, koja su posebice važna u smislu pripreme staništa za prihvat autohtonih vrsta te povećanja otpornosti i plastičnosti šumskih sastojina, što je neizostavna komponenta adaptacijskih strategija gospodarenja šumama. Ipak, daljnja znanstvena istraživanja potrebna su kako bi se kvantificirala uporabljivost svake alohtone vrste, ali i olakšalo donošenje odluka u praksi.

Background and Purpose: Forest damage by wind is an important cause of economic loss in commercial forestry in the Republic of Croatia, as well as in many other European countries. Thus, windthrow resistance of trees represents a significant issue. Spruce forest cultures have shown the lowest resistance to windthrow so far. Nevertheless, there is not much insight into the relationship between trees and stand resistance to wind in the region. The objectives of this paper are to: (i) provide first evidence of the relation between tree characteristics prior to storm event in completely destroyed stands in comparison to slightly damaged stands, (ii) to evaluate the need to consider tree resistance to winds during thinnings, (iii) to evaluate if there is a need for windthrow stability assessment prior to replacement interventions. Materials and Methods: The paper investigates three individual cases of spruce forest cultures on three localities in the hilly part of Central Croatia in the fifth decade of age. Two of three stands were completely destroyed by the storm event during the year 2013. The experiment was established in the spring of 2010 using randomised block design with three replications. Based on total tree height (H) and diameter at breast height (DBH) the following parameters were calculated: wood volume (V), basal area (B) and slenderness coefficient. Descriptive statistics and correlation analyses were made in STATISTICA 8.2. Results: The results show overstocking, unfavourable structure and unfavourable slenderness coefficients (>80:1) in both cultures which were completely destroyed by wind. The correlation among variables revealed a significant relationship for all localities (p<0.05) when slenderness coefficient was compared with B and V (negative), but there was no correlation with H. Conclusions: Research supported the claim that slenderness coefficient and stand structural analysis can be good predictors of damages caused by wind. With respect to the forthcoming increase of frequency and severity of storm events we propose to take evaluation of tree resistance into consideration prior to all silvicultural activities (especially high intensity interventions such as replacement/regeneration). Improved stability of trees against wind should be a silvicultural goal already from the first thinning (higher intensity thinings from below). In the case of unstable stands canopy cover should be opened cautiously to provide the remaining trees an opportunity to slowly respond to space increase. It should be noted that these initial findings should be supported by a more extensive research in the future.

Coppicing has been neglected in recent decades, leaving gaps in knowledge on silvicultural interventions, especially the long-term effects on coppices of Southeast Europe. The recent economic crisis, the sudden increase in energy prices, and the increased demand for assorted wood products have initiated higher interest in coppices in Croatia. Thus, our work aims to define the long-term effects of thinning in sessile oak (Quercus petraea (Matt.) Liebl.) and European beech (Fagus sylvatica L.) sub-mountainous thermophilic low coppices in the Croatian Dinarides. The experiment includes two localities with thinning and control plots. Thinning was performed in 2002, with 17.71% of wood volume removed in the European beech coppice and 26.09% in the sessile oak coppice. In 2020, 1276 trees were marked, measured (DBH, tree height, number of stems per stump), and assessed for vitality, origin, and six silvicultural features revealing tree quality. In 2022, trees were again measured (DBH, tree height) to gain data on tree growth. Conventional data analysis methods were used. The results show a statistically significant positive long-term effect of thinning on tree growth, stem, and crown features and support findings that thinning, by increasing growth and quality, is a necessary intervention in European beech and sessile oak low coppices. Thinning promoted the healthiest and best quality trees/stems, resulting in a more valuable range of wood products and the potential for higher income. It had a positive impact on tree growth regardless of the tree’s origin (seed or stump) and improved the growth and quality of trees among the supporting tree species. Short-term effects of thinning in trial plots suggested that thinning supported tree species diversity, but this effect diminished over time, showing no positive effect after twenty years. The study points to the need for more frequent thinning in coppices to support tree species diversity (i.e., to allow growth to less competitive tree species) but underlines the need for further research.